The pivoting vanes of a given stage are generally controlled by a common device composed of a control ring and connecting rods joined to the control ring and the various vanes and situated around the vanes outside the stator which delimits the gas flow vein through which the vanes extend; the other extremities of the vanes adjacent to the rotor are joined together by an annular mounting. This mounting was traditionally composed of two rings, one upstream and one downstream which were brought together and assembled by bolts so as to enclose the pivots of the vanes and bushes allowing for tilting. This solution tended to be unfavorable owing to the relatively large number of bolts required for assembling the rings and more particularly the resultant weight.
More recently (namely in the French patent 2 556 410), it was suggested to enclose the bushes and joints between the circle sector locking elements whose mounting forms an entire ring and to complete the device by an annular rail, formed in practice of two assembled portions, along which the sectors are threaded and which retain the elements at the desired disposition, despite the centrifugal and other types of forces. This device is lighter but has the drawback of not having any means to retain the vanes along the axis of their pivot, that is in a radial direction of the turbo engine. Thus, there is a need to provide a more complete mounting of the vanes and this is where the invention proves to be satisfactory. It is characterized by an annular structure provided with apertures and added to the sectors supporting the pivots and to the rail supporting the mounting of the sectors, the apertures being formed in such a way so that portions of the annular structure adjacent to them are engaged on throats of the pivots. Thus, the pivots are guaranteed to be interconnected by the annular structure, the throats remaining within the radius of this structure.
Two main embodiments can be distinguished: the annular structure may be separate from the rail or integrated with it. In the first embodiment, the ring is preferably continuous and the apertures have appropriate shapes so that the pivots can be mounted in the ring. The apertures may be slits opening onto one of the sides of the ring or recesses including widened portions via which the intact portions are able to slide not notched by the throats of the pivots. In the second embodiment, the structure may be provided with a double comer section, each comer being composed of a first core rising up from the rail and a second core, the first cores being parallel and the second cores being cocylindrical and directed towards each other from the first cores.